Rotatable substrate supporting mechanism with temperature sensing device for use in chemical vapor deposition equipment

ABSTRACT

A rotatable substrate supporting mechanism for use in a chemical vapor deposition reaction chamber of the type used in producing semi-conductor devices is provided with a susceptor for supporting a single substrate, or wafer, for rotation about an axis normal to the center of the wafer. The mechanism is provided with a temperature sensing system for producing signals indicative of sensed temperatures taken at the center of the susceptor and at various points about the periphery thereof. A gas purging system is provided for inhibiting the flow of reactant gas in unwanted areas of the reaction chamber and in the supporting system itself. Rotational driving of the mechanism is accomplished by a variable speed motor under control of a circuit which stops and starts the rotation at controlled speeds and stops the rotation at a home position for enhancing the handling of the wafers.

This is a division of application Ser. No. 07/330,200 filed Mar. 29,1989, now U.S. Pat. No. 4,996,942 which is a division of applicationSer. No. 07/032,474, filed Mar. 31, 1987, now U.S. Pat. No. 4,821,674,

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to deposition equipment of the typeused for chemical vapor deposition of materials on substrates, and moreparticularly to a rotatable substrate supporting mechanism withtemperature sensing device for use in the deposition chambers of suchequipment.

2. Discussion of the Related Art

In the electronics art, it has long been a practice to employ chemicalvapor deposition equipment for depositing various materials, onsubstrates at high temperatures as part of the process of manufacturingsemi-conductor devices. Basically, chemical vapor deposition equipmentincludes a reaction chamber which is heated to a desired reactiontemperature and is configured for the controlled flow of the materialcarrier gas therethrough. A base, which is commonly referred to in theart as a "susceptor", is located in the reaction chamber for supportingthe substrates upon which the material is to be deposited by the wellknown chemical vapor deposition process.

Prior art susceptors are typically of two basic types with the firstbeing a single planar surface for use in a horizontal attitude and thesecond being an upstanding barrel shaped multi-surface structure. Ineither case, these susceptors are configured to support a multiplicityof relatively small substrates, i.e. in the neighborhood of 2 to 5inches in diameter, for simultaneously depositing materials on themultiplicity of substrates. While simultaneous deposition of materialson a multiplicity of substrates is desirable from a manufacturingstandpoint, it has some drawbacks from a quality standpoint.

The first problem associated with multi-substrate processing relates tothe carrier gas which contains the atoms of the deposition materials. Asthe gas, which may be referred to as a reactant gas, flows over thesurfaces of the substrate and the susceptor, deposition of the materialsresults in changes in the concentration of the deposition materials inthe carrier gas. Consequently, as the reactant gas flows across or overthe length of these relatively large susceptors, across each individualsubstrate and across a multiplicity of such substrates, different ratesof growth of the deposited layer of material have been found. A secondproblem is that of temperature control which is critical at the elevatedtemperatures needed for proper deposition. It is difficult, if notimpossible, to control the temperature within the critical tolerances atall the desired locations within the relatively large reaction chambers.This results in different deposition layer thicknesses from onesubstrate to another, and can even produce varying thickness within theindividual substrates. Still another problem is contamination which canresult from various factors such as the handling techniques used to loadand unload the substrates, the introduction of the carrier gas into thereaction chamber, and indeed from the reaction chamber itself. Thecarrier gas not only deposits the deposition material on the substrate,but also deposition takes place on the walls of the reaction chamber. Inthe relatively large reaction chambers required for multi-substrateprocessing, the unwanted deposits on the walls of the reaction chamberscan be inadvertently incorporated into the growing layers beingdeposited on the substrates.

These problems and drawbacks, as well as other factors, all contributeto significant problems as the semi-conductor devices and the uses towhich they are put become more sophisticated. As a result, many changesand improvements have been made in the equipment that is used tosimultaneously process a multiplicity of substrates. For example, someequipment manufacturers are now using automated loading and off-loadingdevices to eliminate, or at least substantially reduce contaminationresulting from human handling. Further, the second type of susceptordiscussed above, i.e. the upstanding barrel shaped structure, is beingrotated in some instances about its vertical axis to rotate themultiplicity of substrates about that same axis within the reactionchamber. Such barrel rotation is being done for averaging purposes, thatis, temperature averaging and reactant gas flow averaging. Obviouslythese and other things which are being done to improve the simultaneousmulti-substrate processing techniques have helped. However, there arepractical limits which many feel will ultimately make the simultaneousmulti-substrate processing techniques unacceptable or at leastundesirable. One of the limitations is that of the equipment beingadaptable for handling larger diameter substrates. The economics oflarger diameter substrates are causing many manufactures ofsemi-conductor devices to use larger substrates. However, increasing thesize of the substrate is causing some problems with regard totemperature differentials across the substrate, decreasingconcentrations of the deposition material as it is carried across thesubstrate, and the like.

Therefore, steps are being taken now by some equipment manufacturers tomake suitable single substrate processing equipment which issignificantly simpler in so far as controlling the various factorsinvolved in chemical vapor deposition. Single substrate chemical vapordeposition equipment becomes inherently more desirable thanmulti-substrate equipment as the manufactures of semi-conductor deviceschange to larger substrates, i.e. 6 to 8 inches in diameter or evenlarger. One important consideration is the cost at risk when processingone substrate as opposed to the simultaneous multi-substrate processing.That is, if something goes wrong, the monetary loss is far less with onesubstrate that it is with a plurality of substrates. The susceptorsbeing used in single substrate processing equipment consist essentiallyof some sort of platform, or base, for supporting the substrate andcontribute nothing further to the chemical vapor deposition equipment.

Therefore, a need exists for a new and improved susceptor for use insingle substrate chemical vapor deposition equipment which ehances theprocess and thereby helps in eliminating, or at least reducing, theproblems and shortcomings of the prior art.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new and useful rotatablesubstrate supporting mechanism is disclosed for use in single substratechemical vapor deposition equipment. The rotatable substrate supportingmechanism includes a circular susceptor, or platform, for receiving asingle circular substrate and supporting the substrate in the reactantgas flow path through the reaction chamber. The susceptor is providedwith an axially depending driveshaft which is suitably coupled to avariable speed drive means for rotation of the susceptor, and thus thesubstrate, about a vertical rotation axis. By rotating the substrateabout this axis, which is normal with respect to the center of thesubstrate, an averaging of the deposited material growth rates resultsthus overcoming the problem in concentration depletion of the depositionmaterials as the reactant gas flow past the substrate. Rotation of thesusceptor also produces an averaging of the temperature gradient whichresults in a significant reduction in the temperature differences bothin the susceptor and in the substrate being supported thereon.

While the rotatability of the susceptor will inherently improve thetemperature characteristics in comparison to a fixed non-rotatablesusceptor, the substrate supporting mechanism of the present inventionis preferably configured to provide a sophisticated temperature sensingsystem which can be used to produce accurate temperature control in thevicinity of the susceptor. The temperature sensing system includes afirst temperature sensor means which in the preferred embodiment,extends axially and upwardly through the axial driveshaft of thesusceptor for sensing the temperature at the center of the susceptor. Afixed concentric ring is located in close surrounding relationship withthe rotatable susceptor and at least one, and preferably more,additional temperature sensing means are providing at circumferentiallyspaced increments in the fixed ring, and these additional temperaturesensing means will sense the temperatures at various points about therotatable susceptor. Each of the temperature sensing means produces asignal indicative of the sensed temperature, and those signals may becoupled to a suitable control system which operates in conjunction withthe heating system of the reaction chamber for temperature controlpurposes.

Due to the rotation capability of the susceptor and the placement of thefirst temperature sensing means within the axial driveshaft of thesusceptor, the driveshaft must be tubular and the susceptor must beprovided with clearance relative to the reaction chamber. Therefore, themechanism of the present invention is provided with a purging system bywhich a purge gas is introduced under elevated pressure into the tubularshaft which is configured so that the purging gas will emerge from thedriveshaft below the susceptor. In this way, the purge gas will inhibitthe flow of reactant gas into the area below the susceptor and into thetubular shaft and thereby prevent deposited material contamination inthose areas. In addition, the purging gas will inhibit the formation ofhot spots in the mechanism.

In addition to the above, the mechanism of the present invention isprovided with means for vertical adjustment whereby the susceptor, andthus the substrate carried thereon, can be set at an optimum position inthe reactant gas flow path of the reaction chamber. Also, the mechanismis provided with a drive control system by which the rotational speed ofthe susceptor may be adjusted to a desired speed and by which thesusceptor's rotation is stopped at the same point each time forsubstrate handling purposes.

Accordingly, it is an object of the present invention to provide a newand improved substrate supporting mechanism for use in single substratechemical vapor deposition equipment.

Another object of the present invention is to provide a new and improvedsubstrate supporting mechanism having a susceptor, or platform, uponwhich a single substrate is supported in the reactant gas flow path in aheated reaction chamber with the susceptor being rotatable for rotatingthe substrate about an axis which is normal to the center of thesubstrate for temperature and growth rate averaging purposes.

Another object of the present invention is to provide a new and improvedsubstrate supporting mechanism of the above described character whichincludes a temperature sensing means for sensing the temperature atvarious points in and about the rotatable susceptor and producingsignals indicative of the sensed temperatures with the produced signalsbeing usable for temperature control purposes which interacts with theequipment heating system to provide a flat temperature profile acrossthe substrate.

Another object of the present invention is to provide a new and improvedsubstrate supporting mechanism of the above described character whichfurther includes a purging system by which a purge gas under elevatedpressure is introduced into the mechanism to prevent the flow of thereactant gas into the mechanism itself and into the area below therotatable susceptor.

Still another object of the present invention is to provide a new andimproved substrate supporting mechanism of the above described typewherein the substrate supporting susceptor is adjustable along itsrotational axis for optimum locating of the substrate in the reactantgas flow path through the reaction chamber.

Yet another object of the present invention is to provide the abovedescribed substrate supporting mechanism with a drive control system bywhich the rotating speed of the susceptor may be adjustably set to adesired rotation rate and by which the susceptor's rotation is stoppedat the same location each time for improved substrate handling purposes.

The foregoing and other objects of the present invention as well as theinvention itself, may be more fully understood from the followingdescription when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of the substrate supporting mechanism ofthe present invention with the mechanism shown as being used in a typeof reaction chamber which is commonly referred to as a horizontal flowreaction chamber.

FIG. 2 is a view similar to FIG. 1 but showing the substrate supportingmechanism of the present invention as being used in a type of reactionchamber that is commonly referred to as an axial flow reaction chamber.

FIG. 3 is an enlarged elevational view which is partially broken away toshow the various features of the substrate supporting mechanism.

FIG. 4 is an enlarged top view of the substrate supporting susceptor andshowing the concentric relationship of a fixed ring structure which ispart of the temperature sensing system of the mechanism.

FIG. 5 is an enlarged fragmentary sectional view taken along the line5--5 of FIG. 4.

FIG. 6 is an exploded perspective view showing the mounting structuresand arrangement of the susceptor and the fixed ring of the temperaturesensing system of the mechanism of the present invention.

FIG. 7 is a top view of a particular form of susceptor which is providedwith an especially configured top surface upon which a substrate issupportable.

FIG. 8 is a view similar to FIG. 7 but which shows an alternate topsurface configuration provided on the susceptor.

FIG. 9 is a fragmentary sectional view taken along the line 9--9 of FIG.3.

FIG. 10 is a fragmentary view similar to FIG. 3 and showing amodification of the substrate supporting mechanism of the presentinvention.

FIG. 11 is a fragmentary sectional view taken along the line 11--11 ofFIG. 10.

FIG. 12 is a fragmentary sectional view taken along the line 12--12 ofFIG. 10.

FIG. 13 is a schematic drawing of the drive control system of thesubstrate supporting mechanism of the present invention.

FIG. 14 is a fragmentary view similar to FIG. 3 and showing an alternatetemperature sensor embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In that chemical vapor deposition per se is well known in the art, onlya brief description thereof will be presented herein for completeness ofthis disclosure and to ensure full understanding of the presentinvention. Briefly, a reactant gas, which contains gaseous forms of theatoms of the material to be deposited, is introduced into what isreferred to as a reaction chamber in a manner which causes the reactantgas to flow through the reaction chamber in a path which is determinedby reaction chamber configuration, gas injection location and the like.Reaction chambers are heated to relatively high temperatures, which aredetermined by the various factors of the particular process to beaccomplished. By virtue of gas movement, temperature and chemicalreaction, the material carried by the gas will be deposited and adhereto whatever is located in the gas flow path and will provide adeposition layer thereon. This general chemical vapor depositiontechnique is widely used in the electronics art for manufacturingsemi-conductor devices.

Referring more particularly to the drawings, FIGS. 1 and 2 show therotatable substrate supporting mechanism of the present invention whichis indicated in its entirety by the reference numeral 20. FIG. 1 showsthe mechanism 20 as being used in conjunction with a reaction chamber 22of the type sometimes referred to as a horizontal flow reaction chamber,and FIG. 2 shows the mechanism 20 as being used in conjunction with anaxial flow reaction chamber 26. As is known, both horizontal flow andaxial flow reaction chambers have been devised in various configurationsand the particular chambers 22 and 26, which are only partially shown,are intended to be typical representations of such reaction chambers.

It will be noted however, that the reaction chamber 22 has a planarbottom surface 23 with a tubular shaft 24 depending integrallytherefrom, and similarly, the reaction chamber 26 has a planar bottomsurface 27 from which a tubular shaft 28 integrally depends. As willhereinafter be described in detail, the rotatable substrate supportingmechanism is coupled to the depending end of either of the tubularshafts 24 or 28 and portions of the mechanism 20 extend upwardly throughthe axial bores of the shafts into the interior of the reaction chamber22 and/or 26, to provide, among other things, a platform, or susceptor30 upon which a substrate 32 is demountably supportable. The substrate32 is placed on the susceptor 30 prior to commencement of the chemicalvapor deposition process and is off-loaded when the desired depositionfilm, or layer has been formed thereon and the process has beencompleted.

The rotatable substrate supporting mechanism 20 is carried in a mannerwhich will be described in detail below, on a suitable support plate 33which is disposed below the reaction chamber 22 and/or 26. The plate 33is provided with a plurality of bushing mounts 34 (one shown) each ofwhich is slideably movable along a different one of a plurality of fixedvertical rod 35 (one shown). The plate 33, and thus the entire mechanism20, is vertically adjustable relative to the reaction chamber 22 and/or26 by a vertical elevating means 36. The vertical elevating means 36includes a worm gear nut 37 carried on the support plate 33 for movementalong an elongated rotatable worm gear 38. The worm gear 38 is journaledfor rotation about its longitudinal axis in a drive housing 39 that isfixedly carried on a suitable support means 40. The housing 39 containsa suitable gear train such as the illustrated worm gear 41 which isrotatable by means of the hand wheel 42, and the worm gear 41 is indriving meshed engagement with a spur gear 43 (FIG. 1) that is mountedon the lower end of the elongated worm gear 38. Thus, manual rotation ofthe hand wheel 42 in the appropriate direction will, by virtue of thegears 41 and 43, cause the worm gear 38 to be rotatably driven. Suchdriving of the worm gear 38 will cause the worm gear nut 37 to travelalong the worm gear 38 and thereby raise or lower the support plate 33as determined by the direction of rotation of the hand wheel 42.

The above described vertically adjustable elevating means 36 is a coarseadjustment for positioning the susceptor 30 at an optimum positionwithin the reaction chamber 22 and/or 26 and a fine adjustment device isalso provided as will hereinafter be described.

The susceptor 30 is of circular substantially planar configuration andis demountably carried and rotatably driven by a spider structure 44having a central hub 45 from which at least three arms 46 extendradially. Each of the arms 46 is bent or otherwise formed at its distalend to provide an upstanding peg 47 upon which the susceptor 30 issupported. The hub 45 of the spider 44 is provided with a truncatedconical bore 48 in which the tapered upper end 49 of a driveshaftassembly 50 is disposed.

The driveshaft assembly 50 is a multi-piece assembly including anelongated rotation shaft 51 at the uppermost end of the assembly. Therotation shaft 51, having the tapered upper end 49 as mentioned above,is provided with an axial bore 52 for reasons which will become apparentas this description progresses. The rotation shaft 51 has an enlargedtapered lower end 53 of inverted frusto-conical configuration withenlarged diameter upwardly facing annular shoulder 54 in axially spacedrelationship with the lower open end of the shaft.

As is customary in the art, the reaction chambers 22 and 26 arefabricated of a suitable transparent material, such as fused quartz, forthe transmission of heating radiation from a suitable heat source (notshown). Since the depending tubular shafts 24 and 28 depend integrallyfrom their respective reaction chambers 22 and 26, they too are formedof the same transparent material. For the same heat transmission reason,the above described spider structure 44 and the rotation shaft 51 arealso formed of transparent material.

The driveshaft assembly 50 further includes a spindle 56 having an upperbody portion 57 and a lower body portion 58 which may be formed as asingle unitary structure or may be formed as two separate pieces forease of fabrication and joined together such as by welding in the mannerindicated in the drawing. In either case, the upper body portion 57 isof generally cylindrical configuration with a reduced diameter upper end59 which forms an upwardly facing annular shoulder 60 on the upper bodyportion 57. The reduced diameter upper end 59 is provided with externalthreads as indicated at 61 and an axial bore 62 is formed through theupper body portion 57. The axial bore has a tapered socket 64 at itsupper end in which the enlarged tapered lower end 53 of the rotationshaft 51 is seated. A suitable hold-down nut 66 is threadingly carriedon the upper end of the body portion 57 and a wave washer 68, or othersuitable biasing means, is contained within the hold-down nut 66 towedgingly hold the tapered lower end 53 of the rotation shaft 51 in thesocket 64 of the spindle body portion 57. The hold-down nut 66 isprovided with a suitable aperture through which the rotation shaftextends.

For reasons which will hereinafter be described in detail, the upperbody portion 57 of the spindle 56 is further provided with a dependingexternally threaded boss 70 and a plurality (two shown) of passages 72which extend downwardly from the annular shoulder 60 into intersectingrelationship with the axial bore 62 at a location spaced below thetapered socket 64 portion of the axial bore.

The lower body portion 58 of the spindle 56 is of elongated cylindricalconfiguration and defines an axial bore 74 which has an inside diameterthat is considerably larger than the axial bore 62 formed through thespindle's upper body portion 57 and is larger than the outside diameterof the depending boss 70 thereof for reasons which will be explainedbelow. The lower body portion 58 is provided with a reduced diameterlower end 76 and has external threads 77 formed thereon immediatelyabove the point which the diameter of the lower body portion 58 isreduced.

A bearing means, in the preferred form of rotary seal 80, is providedwith a non-rotating portion 81, which is mounted in a manner which willhereinafter be described, and has an elongated rotatable sleeve 82journaled for rotation therein, with the sleeve being axially disposedin the bearing means with a dependingly extending lower end 83 havingexternal threads 84 on the lowermost part of depending end 83. Thedriveshaft assembly 50 is disposed so as to extend coaxially through therotatable sleeve 82 in a manner whereby the sleeve 82 and the driveshaftassembly 50 rotate as a single entity.

Thus, the bearing means 80 is employed in the substrate supportingmechanism 20 to support and rotatably journal the driveshaft assemblyand to prevent gas leakage for reasons which will become apparent asthis description progresses. The bearing means in the form described iscommercially available from the Ferrofludics Corporation of 40 SimonStreet, Nashua, N.H. 03061 and is identified as Model NumberHS-1500-F-W.

A driven pulley 86 is attached, such as by means of the set screw shown,to the dependingly extending lower end 83 of the sleeve 82 and aposition indicator wheel 88 is threadingly mounted immediately below thepulley on the threads 84 provided on the lowermost end of the sleeve 82.Both the driven pulley 86 and the position indicator wheel 88 form apart of a drive means 90 which will hereinafter be described in detail.

A special cage nut 92 having an internally threaded upper portion 93which is threadingly carried on the threads 84 of the sleeve 82 and aninternally threaded lower portion 94 which is threadingly carried on thethreads 77 of the spindle 56. The upper and lower portions 93 and 94 ofthe cage nut 92 are interconnected in axially spaced relationship by atleast two diametrically opposed ribs 95 (one shown) which providedopenings for access to an adjustment nut 96 which is captively retainedbetween the upper and lower portions 93 and 94 of the cage nut 92. Asshown, the adjustment nut 96 is threadingly mounted on the threaded end77 of the spindle 56. Manual rotation of the adjustment nut 96 willaxially slideably move the entire driveshaft assembly 50 relative to thesleeve 82 of the rotary seal bearing means 80, and this is used to makethe above mentioned fine vertical adjustments of the susceptor 30 in thereaction chamber 22 and/or 26.

The substrate supporting mechanism 20 is carried on the above mentionedsupport plate 33 which has an opening 100 formed therethrough. Anadjustment plate 102 is mounted atop the support plate 33 and isprovided with an opening 104 which is substantially coaxial with respectto the opening 100 of the support plate. The adjustment plate 102 isconnected to the support plate 33 by a suitable bolt 105 about which theplate 102 is pivotably movable for adjustable location in a horizontalplane of the opening 104. The adjustment plate 102 is lockable in thedesired position by a diametrically opposed bolt 106 and washer 107 withthe bolt 106 passing downwardly through an enlarged aperture 108 of theplate 102 into threaded attachment with the support plate 33. A bearingmounting plate 110 having an opening 111 formed therethrough ispositioned atop the adjustment plate 102 and is configured to provide anaxially depending reduced diameter boss 112 which extends approximatelyhalf way down into the opening 104 of the adjustment plate 102. Thenon-rotating portion 81 of the bearing means 80 is bolted fast to thelower surface of the boss 112 so that it extends approximately half wayup into the opening 104 of the adjustment plate 102. The bearingmounting plate 102 is mounted in place by the bolt 105 and others (notshown) which, as previously discussed, are used to fix the adjustmentplate 102 on the support plate 33. In addition to supporting the bearingmeans, the bearing mounting plate 110 is adjustably tiltable by means ofthe adjustment screw 113 which depends from the seal mounting plate 110into bearing engagement with the upper surface of the adjustment plate102. From the above, it will be seen that the adjustment plate 102 andthe bearing mounting plate 110 are independently adjustable andcooperatively interact to provide the properly aligned coaxial andvertical relationships of the bearing 80 and the driveshaft assembly 50.

A coupling plate 114 is positioned atop the bearing mounting plate 110and is free to float into aligning relationship with the bearingmounting plate 110 and the depending tubular shaft 24 and/or 28 of thereaction chambers 22 and 26 respectively. Once the aligned relationshiphas been established, such as during initial assembly of the substratesupporting mechanism 20, the coupling plate 114 may be tightened downagainst any further additional movement such as by means of theillustrated bolt 116, and others (not shown). The coupling plate 114 isformed with an axially upwardly extending externally threaded boss 118,and an axial bore 120 is formed through the coupling plate. An O-ringseal 122 is provided at the upper end of the boss 118 so as to be insealed circumscribing engagement with the peripheral surface of thedepending tubular shaft 24 or 28. A clamping nut 124 having an axiallyopening 125 formed therethrough is threadingly carried on the boss 118to exert a circumferentially compressive force on the O-ring seal 122 byvirtue of a compressing ring 126 carried in the clamping nut.

A heat sensing means in the preferred form of a thermocouple 130 ismounted in the upper end of a sheath 132 formed of suitable heatresistant material. The sheath 132 is of elongated configuration and isopen on the end 133 thereof which is opposite to the closed end in whichthe thermocouple 130 is contained, with the open end being provided forexiting of the thermocouple wires 134 from the sheath. The lower endportion of the sheath 132 is axially disposed in a tube 136 having afitting means 138 on its upper end and having a nut 140 on its lowerend. The tube 136 and its associated fitting 138 and nut 140, is used toinstall and hold the sheath 132 in the axial bore that is cooperativelyformed by the bores of the various components which make up thedriveshaft assembly 50. As shown, the fitting means 138 is threadinglyattached to the depending boss 70 of the upper body portion 57 of thespindle 56, and a suitable O-ring seal 142 is provided at the junctionof the fitting means 138 and the boss 70 to prevent gas leakagedownwardly through the tube 136 as will hereinafter be described. Thelower end, that is, the nut 140 extends below the open bottom end of thespindle 56 and is used simply as a tool for attaching the upper endfitting of the tube to the boss 70.

As shown, the upper closed end of the sheath 132 extends from the bore52 of the rotation shaft 51 upwardly into a blind central cavity 144formed in the lower surface of the susceptor 30. In this way, thethermocouple 130 will sense the temperature at the center of thesusceptor 30 and produce an electric signal indicative of the sensedtemperature in the manner well known in the art. The thermocouple 130forms part of a temperature sensing system of the substrate supportingmechanism 20 as will hereinafter be described in detail.

In that the sheath 132 is axially carried in the driveshaft assembly 50as described above, it will rotate along with the driveshaft assembly.For this reason, a slip-ring means 146 is provided on the lower end ofthe substrate supporting mechanism 20. The slip-ring means 146 iscommercially available from the IEC Corporation, 3100 LonghornBoulevard, Austin, Tex. 78759, and is a sealed unit identified as ModelNo. IECFCS. The slip-ring means 146 has an axial sleeve 148 thereinwhich is coupled by means of a clamping nut 150 to the reduced diameterlower end 76 of the spindle 52 for rotation therewith. The lower reduceddiameter end 76 of the spindle 56 extends axially through the sleeve 148of the slip-ring means 146, and the lower end of the sleeve 148 iscoupled, such as by a pin 152 to the rotatable outer portion 154 of theslip-ring means. The slip-ring means 146 has a fixed core 156 which iscoaxially disposed between the inner sleeve 148 and the rotatableportion 154. The core 156 is fixed against rotation by means of a flange158 that is suitably attached to the upper end of the core 156 and isalso attached by bolts 160 to the lower end of a housing 162.

The thermocouple wires 134 which extend from the sheath are connected bymeans of a suitable plug 164 to the wires 166 which extend from therotatable outer portion 154 of the slip-ring means 146. The electricsignal produced by the thermocouple 130 is thereby transmitted via thewires 134 and 166 to the rotatable portion of the slip-ring means 146,and by the well known slip-ring method, are conducted to the fixed core156 thereof. The signal received in the fixed core 156 is coupled bysuitable wires 168 extending from the core 156 to a point of use (notshown).

The housing 162 is of cylindrical open ended configuration defining abore 170 with a counterbore 171. The housing 162 is suspendingly carriedby the rotary bearing means 80 such as by means of the bayonettemounting arrangement 172 shown in FIGS. 1 and 2, and the split clamps173 and 174 shown best in those same figures.

In that the reaction chambers 22 and/or 26 are provided with thedepending tubular shafts 24 and 28 and the driveshaft assembly 51 istubular, the rotatable substrate supporting mechanism 20 is providedwith a purging system by which the reactant gas, and deposition materialcarried thereby, through the reaction chamber, will be prevented fromflowing into the area below the susceptor 30 and downwardly into themechanism 20.

As shown in FIG. 3, the bearing mounting plate 110 is provided with apassage 176 one end of which opens into the bore 111 thereof, with theother end being provided with means 178, such as the fitting shown, fordirecting a suitable purge gas under elevated pressure from an externalsource (not shown) into the bore 111 of the bearing mounting plate. Agas restrictor housing 180 is mounted in the bore 111 of the bearingmounting plate 110 and is configured to have an inverted cup-shaped body182. The body 182 is provided with an annular groove 183 which alignswith the inwardly opening end of the passage 176 for receiving the purgegas therefrom. A plurality of incrementally spaced injection ports 184extend from the annular groove 183 radially into the cavity 186 definedby the cup-shaped body 182. In that the body 182 opens downwardly, thepurge gas received in the cavity 186 will flow downwardly into theannular recess between the reduced diameter upper end 59 of the spindle56 and the upper end of the sleeve 82 of the rotary bearing means 80.The gas received in that annular recess will flow through the passages72 of the spindle 56 into the bore 62 of the spindle. By virtue of theO-ring seal 142 which sealingly separates the lower end of the bore ofthe driveshaft assembly 51 from the upper end thereof, the purge gasreceived from the passages 72 will flow upwardly in the bore 62 of thespindle 56 into the bore 52 of the rotation shaft 51. In that the topend of the rotation shaft 51 is open so that the thermocouple sheath 132can extend therefrom to the susceptor 30, upwardly flowing purge gaswill exit the rotation shaft 51 under the central portion of thesusceptor 30.

The gas restrictor housing 180 further includes a boss 188 which extendsaxially upwardly from the cup-shaped body 182 and defines a bore 190through which the rotation shaft 51 axially extends. The outsidediameter of the rotation shaft 51 is smaller than the inside diameter ofthe bore 190 to provide an annular gap therebetween. Therefore, some ofthe purge gas received in the cavity 186 will flow upwardly through thatannular gap into the bore of the tubular shaft 24 or 28 of the reactionchambers 22 or 26, and that gas will flow upwardly into the area belowthe susceptor 30.

A suitable bracket means 192 is mounted so as to depend from the supportplate 33 and a variable speed DC motor 194 is carried by the bracket. Adrive pulley 195 is mounted on the output shaft 196 of the motor, and abelt 198 is employed to transmit rotary power from the DC motor 194 tothe driven pulley 86 carried on the driveshaft assembly 50 of thesubstrate supporting mechanism 20.

As indicated in phantom lines in FIG. 4, most, if not all, substratesare provided with a notch 199 for orientation purposes. For this reason,it is desirable that the susceptor 30 be stopped at the same point inits rotation each time that it is stopped for placement and removal of asubstrate. Therefore, the position indicator wheel 88, which washereinbefore mentioned as being part of the drive means 90, is providedwith a circular base 200 to which a nut 201 is demountably attached,such as by means of the illustrated threaded engagement, to hold anindex means 202 therebetween. The index means 202 preferably includes apair of ring-shaped plates 203 and 204 which are in contiguous coaxialengagement with each other. As shown in FIG. 9, the upper plate 203 hasa notch formed in its peripheral edge and the lower plate 204 has asimilar notch. The two plates 203 and 204 may be adjustably rotatedrelative to each other so that the notches thereof cooperatively form aslot 206 which is adjustably variable as to its length. This adjustmentfeature of the index means 202 is desirable to provide the rotatablesusceptor mechanism 20 with the capability of being repeatedly stoppedat the same place, i.e. home position, regardless of the rotational homespeed at which the mechanism is to be driven. However an index meanshaving a fixed size slot (not shown) may be used whenever a singlerotational home speed is to be used, as will hereinafter be described.

The index means 202 is disposed so that the variably sized slot 206thereof is rotatably driven through a groove 207 formed in thebifurcated end of a sensor switch 208. The sensor switch 208 is carriedin a suitable mounting bracket 210 which is bolted or otherwise attachedto the housing 162 so that the bifurcated end of the switch 208 extendsradially into the interior of the housing 162 and straddles therotational path of the index means 202 of the position indicator wheel88.

Reference is now made to the schematic wiring diagram of FIG. 13 whichshows the various components which cooperatively form a control system212 for driving the rotatable substrate supporting mechanism 20. Firstof all, a suitable programmable input system 214, which is not part ofthe control system 212, except for its supplying of an input signalhaving a predetermined time duration, is used to adjustably determine,among other things, the length of time of a mechanism cycle. The inputsystem 214 applies an input signal, i.e. a voltage, via a conductor 215to a junction point 216 so that the voltage is simultaneously applied bya conductor 217 to the first terminal of voltage comparator 218 and by aconductor 219 to a potentiometer P1. The potentiometer P1 is adjustablyset for determining the normal rotational speed of the mechanism 20, inotherwords, the input system 214 cannot drive the mechanism 20 at speedsabove that set by the potentiometer P1. The output voltage from thepotentiometer P1 provides a first control signal which is directedthrough a two position contactor 220 of a relay R1 and through aresistive-capacitive network 221 (RC) by a conductor 222 which appliesthat voltage to a suitable amplifier 223. The amplified voltage isdirected by a conductor 224 to the variable speed DC motor 194 fordriving the driveshaft means at a relatively high speed.

A second potentiometer P2 is used to apply an adjustably variablevoltage to the second input terminal of the above mentioned voltagecomparator 218. The comparator 218 is non-conductive when the voltagevalue from the input system 214 is above the voltage value applied bythe potentiometer P2. In otherwords, when the voltage from the inputsystem 214 is at a relatively high value, for producing normalrotational speed of the motor 194, the comparator 218 will benon-conductive. However, when the voltage from the input system 214begins to decrease in value, indicative of an end of a cycle of themechanism 20, the comparator 218 will be enabled when the voltage fromthe input system 214 drops in value below that applied by thepotentiometer P2. When the comparator 218 is enabled, a voltage at itsoutput terminal will be coupled by conductor 225 to the relay R1, forenergizing thereof. When the relay R1 is energized in this manner, itwill move the two position contactor 220 out of its normal position intocontact with the terminal 226, and simultaneously close the normallyopen contactor 227 thereof. When the two-position contactor 220 is movedinto contact with the terminal 226, the output voltage from a thirdpotentiometer P3 provides a second control signal which is coupledthrough the RC network 221, the amplifier 223 to the D.C. motor 194. Thepotentiometer P3 is adjustably set to a voltage value which is less thanthat of the output value of the potentiometer P1 for rotatably drivingthe mechanism 20 at a reduced, or "home" speed.

The above mentioned sensor switch 208 is an optical device including aphotoemitter diode 230 and a normally open photoreceptor transistor 232on opposite sides of the index means 202 of the position indicator wheel88. When the slot 206 of the index means 202 is rotated into positionbetween the photoemitter diode 230 and the photoreceptor transistor 232,impinging light will render the photo transistor 232 conductive. Whenenabled in this way, the supply voltage applied to the input terminal ofthe photo transistor 232 by conductor 234, will pass through thecontactor 227, which was closed upon energization of the relay R1, andwill energize another relay R2. When the relay R1 is energized it willclose its contactor 236 which completes a grounding circuit at the inputof the amplifier 223 to drop the voltage at the input to zero thusstopping the motor 194.

The RC network 221 of the control system 212 is a time constant circuitwhich is used to control start-up and slow-down speeds of the rotationaldrive of the mechanism. In otherwords, the start-up and slow-down speedsmust not be too abrupt or the substrate carried on the susceptor couldbe dislodged. Thus, the RC network produces in a well known manner,relatively smooth build-up or ramp, in the applied voltages to the motor194, and a relatively smooth decrease or ramp, in those voltages whenthey are being removed from the motor 194.

While the control system 212 is preferably provided with thepotentiometers P1, P2 and P3 for adjustable versatility of the mechanism20, it will be understood than in most applications, fixed value voltagedropping resistors (not shown) could be used.

As indicated in FIG. 6, the susceptor 30 may be provided with a smoothplanar upper surface 240 upon which a substrate to be processed issupportable. However, due to rotation of the susceptor and the flow ofgas through the reaction chamber 22 and/or 26, it is preferred that thesusceptor be formed with a non-smooth upper planar surface forpositional stability of the substrate. In a first modified susceptor 30Ashown in FIG. 7, a circular central recessed area 242 is provided forreceiving a substrate and retaining it in the desired position within acircular rim 244. In a second modified susceptor 30B shown in FIG. 8,the upper surface 246 has a plurality of concentric grooves 248 ofvarying diameters, and a plurality of radially extending channels 250formed therein. The grooves 248 and channel 250 cooperatively interactto allow the free flow of gasses between the substrate and the susceptorduring placement and removal of the substrate to prevent undesiredslipping movement of the substrate.

As hereinbefore mentioned, the substrate supporting mechanism 20includes a temperature sensing system with the hereinbefore describedheat sensing means 130 forming a part thereof. The temperature sensingsystem further includes a fixed ring structure 252 which is supported insubstantially surrounding concentric relationship relative to thesusceptor 30. The ring structure 252 is supported in upwardly spacedrelationship with respect to the bottom surface 23 or 27 of the reactionchambers 22 or 26 by a stand 254 which is preferably formed oftransparent material. The stand 254 as best seen in FIG. 6, has amulti-sided substantially ring-shaped rail 256 having depending feet 258for resting on the bottom surface of the reaction chamber and upstandingpins 260 for supporting the ring structure 252 in a fixed non-rotatingposition. Although the stand 254 is shown as being of a fixed heightrelative to the bottom surface of the reaction chamber(s), that heightmay be change such at the time of manufacture, by employing feet and/orpins of different lengths.

As shown in FIGS. 4 and 5, the fixed ring structure 252 includes aninner ring body 262 and an outer ring body 264 which cooperativelydefine an annular passage 266 about the ring structure. In theillustrated embodiment, three temperature sensing means 268, 270, and272 are shown as being disposed at various locations in the annularpassage 266 of the ring structure 252. It will be understood that as fewas one temperature sensing means can be employed or a multiplicity canbe used as necessary to achieve the desired temperature sensingcapability. It has been found that in horizontal flow reaction chambers,such as the one indicated at 22 in FIG. 1, the three temperature sensingmeans 268, 270, and 272 provide ideal temperature sensing capabilitieswhen used in conjunction with the previously described temperaturesensing means 130. As indicated by the arrow 274 in FIG. 4, the gascarrying the desired deposition materials, will flow across the ringstructure 252 in a direction from what may be considered as the leadingedge 276 to the trailing edge 278. The temperature sensing means 268 islocated at the leading edge 276 to sense the temperature at that point.The temperature sensor means 130 will, as hereinbefore described, sensethe temperatures at the center of the rotatable susceptor 20, and theother two temperature sensor means 270 and 272 will sense thetemperature proximate the trailing edge 278 of the ring structure 252.The temperature sensing means 268, 270, and 272 are preferably of thesame configuration as the previously described temperature sensor means130. That is, the temperature sensor means are in the preferred form ofthermocouples each of which is mounted in a sheath 280 of transparentmaterial. The sheaths 280 of each of the thermocouples 268, 270, and 272are of elongated configuration and extend from the ring structure 252via suitable apertures 282, 283, and 284 formed through the outer ringbody 264. In this way, the conductive wires 286, 288, and 290 of thethermocouples 268, 270, and 272 respectively, extend out of the hostileenvironment of the susceptor 20 and ring structure 252. The electricsignals produced by the thermocouples 120, 268,270, and 272 are coupledto a suitable temperature control device (not shown) which forms no partof the substrate supporting mechanism 20 of this invention.

Reference is now made to FIGS. 10, 11 and 12 wherein a modified form ofthe rotatable substrate supporting mechanism is shown and is indicatedgenerally by the reference numeral 20A. The mechanism 20A is essentiallythe same as the previously described mechanism and has a modified formof gas restrictor housing 294 mounted in the bore 111 of the bearingseal mounting plate 110. The gas restrictor housing 294 has an invertedcup-shaped body 296 with the annular groove 298 and injection ports 299for receiving the purge gas from the passage 176 of the seal mountingplate 110. The purge gas is directed into the downwardly opening cavity300 of the gas restrictor housing 294, for movement downwardly and thenupwardly into the bore 52 of the rotation shaft 51 in the mannerhereinbefore fully described with reference to the mechanism 20. Themodified gas restrictor housing 294 of the mechanism 20A has anelongated tube 302 extending axially upwardly therefrom. The rotationshaft 51 extends axially through the tube 302 which is sized to providean annular gap 304 between the outside diameter of the rotation shaft 51and the inside diameter of the tube 302 of the gas restrictor housing294. Therefore some of the purge gas received in the cavity 300 of thegas restrictor housing 294 will flow upwardly through the annular gap304 and emerge from the tube 302 below the susceptor 30.

The uppermost end of the tube 302 of the gas restrictor housing 294 issuitably configured to carry a stand means 306 preferably of transparentmaterial upon which the ring structure 252 is supported. The stand means306 includes a disc shaped body 308 having at least three arms 310extending therefrom. Each of the arms 310 is provided with an upstandingpin 311 upon which the fixed ring structure 252 is carried.

By mounting the ring structure 252 on the stand means 306, rather thanthe stand 254 of the mechanism 20, the stand means 306, and thereby thering structure 252 and the temperature sensing means 268, 270, and 272(FIG. 4) carried thereby, are vertically adjustable along with thesusceptor 30 as hereinbefore described with reference to the mechanism20.

The modified form of substrate supporting mechanism 20A further includesa modified coupling plate 312 which, as in the case of the previouslydescribed coupling plate 114, is free to float into aligningrelationship with the bearing mounting plate 110 and the dependingtubular shaft 24 and/or 28 of the reaction chamber 22 or 26. Thecoupling plate 312 is provided with an axially upwardly extendingexternally threaded boss 314 defining an axial bore 316. The clampingnut 124, is threadingly carried on the boss 314 for exerting acircumferentially compressive force on the O-ring seal 122 by virtue ofthe compression ring 126 carried in the clamping nut 124. Purge gas,from an external source is supplied to a passage 318 formed in thecoupling plate 312 such as through a suitable fitting means 320 so thatthe purge gas is directed into the counterbored lower end 322 of thecoupling plate 312 and will flow upwardly in the annular space 324between the depending tubular shaft 24 or 28 of the reaction chamber 22or 26, and the elongated tube 302 of the gas restrictor housing 294.

Therefore, in the modified substrate supporting mechanism 20A thepurging gas will flow upwardly through the rotation shaft 51, throughthe annular gap 304 between the rotation shaft 51 and the upstandingtube 302 of the gas restrictor housing 294, and through the annularspace 324 discussed above.

The free floating coupling plate 114 of the first embodiment of thepresent invention was described as being bolted in a fixed positionsubsequent to its having been positioned in the desired alignedposition. In many reaction chamber installations, such bolting in placemay not be able to be accomplished due to the inability to reach thenecessary points for accomplishing such bolting. Therefore, the modifiedmechanism 20A is shown as including an automatic clamping device 326.

The clamping device 326 includes a lever 328 which is pivotably carriedon a suitable pin 330. The pivot pin 330 is mounted in clevis 332 whichis mounted atop the support plate 33A, and a depending lug 334 ismounted on the lever 328 with the pivot pin 330 passing through asuitable aperture provided in the lug. One end 336 of the lever 328extends away from the mechanism 20A and a suitable adjustment screwassembly 338 is carried in that end 336 of the lever. An electrically,pneumatically, or otherwise operated actuator mechanism 340 is mountedin the support plate 33A, and is operable for extending and retractingmovement of an actuator pin 342. When actuated, such as at the beginningof an operational cycle, or cycles, of the mechanism 20A, the actuatorpin 342 will move to its illustrated extended position and produce acounterclockwise pivot movement of the lever 328, as viewed in FIG. 10.

The other end 344 of the lever 328 is bifurcated to provide a pair ofspaced aprt arms 346 which are stradlingly disposed on diametricallyopposed sides of the upwardly extending boss 314 of the coupling plate312. Each of the arms 346 is provided with a depending pin 348 whichwill bear down on the coupling plate 312 when the lever 328 is pivotablymoved in the manner hereinbefore described. When the clamping force isapplied to the coupling plate 312 a compressive force will be applied tothe O-ring seals 350 to prevent gas leakage between the coupling plate312 and the bearing mounting plate 110.

Reference is now made to FIG. 14 wherein a modified form of therotatable substrate supporting mechanism is shown with the modifiedconfiguration being indicated in its entirety by the reference numeral20B. The mechanism 20B, which may be identical to the hereinbeforedescribed mechanisms 20 or 20A with the exception of the changesdiscussed below, includes a modified susceptor 30B which is providedwith a central aperture 360 rather than the blind cavity 144 mentionedin the previous embodiments. The driveshaft assembly 50B includes therotation shaft 51 with a modified spindle 56B. The spindle 56B includesthe upper portion 57 and a modified lower portion 58B which has adepending boss 362 on its lower end which is externally threaded asshown.

The drive shaft assembly 50B defines an axial passage 364 which in thisembodiment, is used for the transmission of radiated heat from thecenter of the substrate 32 and is, therefore left open. The radiatedheat enters the axial bore, or passage, 364 through the central aperture360 of the susceptor 30B, and is transmitted by radiation to a windowmeans 366 which is carried on the depending boss 362 of the drive shaftassembly 50B. A suitable mounting means 368, such as the illustratednut, is used to mount the window means 366 on the drive shaft assemblyfor rotation therewith. The window means 366 includes a lens 370 whichis formed of a material such as magnesium to the particular wavelengthof radiated heat and are not dependent on the temperature for theirtransparency. The lens 370 is mounted in a suitable ring 372 and iscarried by the mounting means 368 with a suitable O-ring gasket 374 isemployed to prevent the passage of purge gas around the window means366. The radiated heat passing through the window means 366 is sensed bya radiation pyrometer 376 of a type well known in the art, whichproduces an electric signal indicative of the sensed temperature.

While the principles of the invention have now been made clear in theillustrated embodiments, there will be immediately obvious to thoseskilled in the art, many modifications of structure, arrangements,proportions, the elements, materials and components used in the practiceof the invention and otherwise, which are particularly adapted forspecific environments and operation requirements without departing fromthose principles. The appended claims are therefore intended to coverand embrace any such modifications within the limits only of the truespirit and scope of the invention.

What we claim is:
 1. A mechanism for demountably supporting a singlesubstrate in the reactant gas flow path of a chemical vapor depositionreaction chamber, which reaction chamber has a bottom surface and atubular shaft depending from the bottom surface, said mechanismcomprising in combination:a) drive shaft means defining a rotationalaxis, said drive shaft means being coaxially located within the tubularshaft and having a top end extending upwardly from the tubular shaftinto the reaction chamber and having a lower end depending from thetubular shaft; b) drive means coupled to the lower end of said driveshaft means for rotating said drive shaft means; c) a susceptor defininga top surface for demountably and concentrically receiving thesubstrate, said susceptor being coupled to said drive shaft means torotate in response to rotation of said drive shaft means and supportedin a position wherein the rotational axis of said drive shaft means isnormal with respect to the center of said susceptor, said susceptorhaving a central aperture; d said drive shaft means including an axialbore for receiving radiant heat through the aperture of said susceptorwhen the substrate is mounted upon said susceptor and for transmittingthe radiant heat through the axial bore; e) window means disposed on thelower end of said drive shaft means for sealingly closing the lower end,said window means being transparent to the wavelengths of the radiantheat transmitted through the axial bore; and f) a radiation pyrometerfor sensing the temperature of the radiant heat transmitted through saidwindow means and for producing a signal indicative of the sensedtemperature sensed.
 2. A mechanism as claimed in claim 1 wherein saidwindow means includes a lens formed of magnesium fluoride.
 3. Amechanism as claimed in claim 1 wherein said window means includes alens formed of calcium fluoride.
 4. A mechanism as claimed in claim 1and including a remote source of purge gas and means for directing thepurge gas upwardly through the tubular shaft and through the axial boreto inhibit the flow of reactant gas into the area below said susceptor,into the tubular shaft and into the axial bore.
 5. A mechanism fordemountably supporting a single substrate in the reactant gas flow pathof a chemical vapor deposition reaction chamber, which reaction chamberhas a bottom surface and a tubular shaft depending from the bottomsurface, said mechanism comprising in combination:a) drive shaft meansdefining a rotational axis, said drive shaft means being coaxiallylocated within the tubular shaft and having a top end extending upwardlyfrom the tubular shaft into the reaction chamber and having a lower enddepending from the tubular shaft; b) drive means coupled to the lowerend of said drive shaft means for rotating said drive shaft means; c) asusceptor defining a top surface for demountably and concentricallyreceiving the substrate, said susceptor being coupled to said driveshaft means to rotate in response to rotation of said drive shaft means;d) a support plate placed in downwardly spaced relationship with respectto the reaction chamber and having an opening coaxial with said driveshaft means; e) mounting means disposed on said support plate forattachment to the tubular shaft, said mounting means defining an axialopening coaxial with the opening of said support plate and for receivingsaid drive shaft means; and f) bearing means depending from saidmounting means and in circumscribing engagement with said drive shaftmeans for supporting and journaling said drive shaft means.
 6. Amechanism as claimed in claim 5 and further comprising:a) said mountingmeans including a coupling means for positioning the axial opening ofsaid mounting means in communication with the inside of the tubularshaft; b) said mounting means including an elongated tube extendingaxially upwardly in spaced coaxial relationship with said drive shaftmeans and within the tubular shaft, said elongated tube having a topend; c) stand means attached to the top end of said elongated tube; d) aring structure means supported on said stand means in a fixed positionin concentric surrounding relationship with said susceptor; and e) atleast one temperature sensing means disposed in said ring structuremeans for sensing the temperature at a point on said ring structuremeans proximate the periphery of said susceptor and for producing asignal indicative of the temperature sensed.
 7. A mechanism as claimedin claim 6 and further comprising:a) said drive shaft means including anaxial bore; and b) temperature sensing means disposed in a spacedcoaxial position within the axial bore, said temperature sensing meansextending from the top of the axial bore into the vicinity of the centerof the bottom of said susceptor for sensing the temperature at thecenter of said susceptor and for producing a signal indicative of thetemperature sensed.
 8. A mechanism as claimed in claim 5 and furthercomprising:a) said susceptor including a central aperture; b) said driveshaft means including an axial bore for receiving radiant heat from thecenter of the substrate transmitted through the aperture of saidsusceptor when the substrate is mounted upon said susceptor; c) windowmeans disposed at the lower end of said drive shaft means for sealinglyclosing the axial bore, said window means being transparent to thewavelengths of the transmitted radiant heat; and d) a radiationpyrometer for sensing the temperature of the radiant heat transmittedthrough said window means and for producing a signal indicative of thetemperature sensed.
 9. A mechanism as claimed in claim 8 and furthercomprising, said mounting means including means for receiving a purgegas under elevated pressure from a remote source and for directing thepurge gas upwardly through the tubular shaft of the reaction chamber,through said elongated tube and through the axial bore to inhibit theflow of reactant gas into an area below said susceptor, into the tubularshaft, into said elongated tube and into the axial bore.
 10. A mechanismfor demountably supporting a single substrate in the reactant gas flowpath of a chemical vapor deposition reaction chamber, which reactionchamber includes a bottom surface having a tubular shaft dependingtherefrom, said mechanism comprising:a) drive shaft means defining arotational axis, said drive shaft means being coaxially placed withinthe tubular shaft and having a top end extending upwardly from thetubular shaft and into the reaction chamber and a lower end dependingfrom the tubular shaft; b) a support plate located downwardly of thereaction chamber and having an opening coaxial with said drive shaftmeans; c) mounting means disposed on said support plate for attachmentto the tubular shaft of the reaction chamber, said mounting meansdefining an axial opening coaxial with the opening in said support platefor penetrably and axially receiving said drive shaft means; d) bearingmeans attached to said mounting means in circumscribing engagement withan intermediate portion of said drive shaft means for supporting androtatably journaling said drive shaft means; e) drive means coupled tosaid drive shaft means for rotating said drive shaft means; and f) asusceptor having a top surface for demountably receiving the substratein a position substantially aligned overlying relationship with thecenter of said susceptor, said susceptor being coupled to said driveshaft means to rotate about the rotational axis of said drive shaftmeans.
 11. A mechanism as claimed in claim 10 and further comprisingspider means disposed on the top of said drive shaft means for couplingsaid susceptor with said drive shaft means.
 12. A mechanism as claimedin claim 11 and further comprising:a) said mounting means including acoupling means for sealingly attaching said mounting means with thetubular shaft, the axial opening of said mounting means being incommunication with the inside of the tubular shaft; b) said mountingmeans further including an elongated tube extending axially upwardly inspaced coaxial relationship with said drive shaft means, said elongatedtube having a top end disposed between the bottom surface of thereaction chamber and said spider means; c) stand means attached to thetop end of said elongated tube; d) a ring structure means supported onsaid stand means in a fixed position concentric with said susceptor; ande) at least one temperature sensing means disposed in said ringstructure means for sensing the temperature at a point on said ringstructure means proximate the periphery of said susceptor and forproducing a signal indicative of the temperature sensed.
 13. A mechanismas claimed in claim 12 and further comprising:a) said susceptorincluding a central aperture; b) said drive shaft means including alower end and an axial bore for receiving radiant heat from the centerof the substrate through the aperture of said susceptor and fortransmitting the radiant heat; c) window means disposed on the lower endof said drive shaft means for sealingly closing the axial bore, saidwindow means being transparent to the wavelengths of the radiant heattransmitted through the axial bore; and d) a radiation pyrometer forsensing the temperature of the radiant heat transmitted through saidwindow means and for producing a signal indicative of the temperaturesensed.
 14. A mechanism as claimed in claim 13 wherein said window meansincludes a lens formed of magnesium fluoride.
 15. A mechanism as claimedin claim 13 wherein said window means includes a lens formed of calciumfluoride.
 16. A mechanism as claimed in claim 13 and furthercomprising:a) said drive shaft means including passage means extendingfrom the axial bore to the axial opening of said mounting means; and b)said mounting means including means for receiving a purge gas atelevated pressure from a remote source and for directing the purge gasupwardly through the tubular shaft, through said elongated tube andthrough the axial bore of said drive shaft means for inhibiting the flowof reactant gas into the area below said susceptor, the tubular shaft,said elongated tube and the axial bore of said drive shaft means.